The present invention relates to an airbag device for protection of a vehicle occupant and, more particularly, to an airbag that is inflatable in front of a vehicle occupant.
Airbags are employed in various locations in vehicles as secondary restraint mechanisms to operate in conjunction with seat belts in order to provide enhanced protection for vehicle occupants during an impact event. A front impact airbag typically is designed to inflate over a 15-40 millisecond time frame, and to deflate in a controlled manner as the occupant moves forwardly against the inflated airbag to absorb kinetic energy.
Some front airbags are designed to inflate partially in the case of an out-of-position occupant, such as an occupant who at the time of the impact event is leaning forwardly, or in other situations where the occupant is too close to the airbag module for proper airbag deployment. Such arrangements are intended to reduce the inflation force so that the closely positioned occupant is not injured by the expanding airbag. Examples of such devices are mentioned briefly below.
U.S. Pat. Nos. 5,709,405, 6,161,866, 6,199,895 and 6,746,044 disclose airbag devices in which an electronic control system operates a mechanical vent valve. Valve actuation is governed by an occupant position sensor. When an out-of-position occupant condition is detected, a portion of the inflation gas is vented from the casing of the device to moderate the degree of airbag inflation.
U.S. Pat. No. 5,280,953 discloses an airbag having side vents that are progressively closed by a tether-actuated sliding flap as the airbag inflates. The degree of vent closure depends on the displacement of the airbag toward the fully deployed position.
US patent publication No. US 2004/0188990 A1 discloses various tether-actuated valve arrangements that close a gas vent channel in the airbag module casing as the airbag approaches the fully deployed position.